<mat-sidenav-container>
    <mat-sidenav #sidenav mode="side">
        <app-sidebar></app-sidebar>
    </mat-sidenav>
    <div class="site">
        <header>
            <app-header (toggle)="sidenav.toggle()"></app-header>
        </header>
        <main>
        </main>
        <footer>
            <app-footer> </app-footer>
        </footer>
    </div>
</mat-sidenav-container>